Binary storage element



June 10, 1958 J. c. CHU

BINARY STORAGE ELEMENT I Filed May l5, 1953 2 Sheets-Sheet 2 on C INVENTOR Jeffrey 62 6/74:

United States Patent BINARY STORAGE ELEMENT Jctfrey C. Chu, Naperville, Ill., assignor to the United States of America as represented by the United States Atomic Energy Commission Application May 15, 1953, Serial No. 355,352

Claims. (Cl. 250-"-27) The present invention relates to electronic computing circuits and more especially to a binary storage device comprising a. toggle or storage element provided with associated improved driver circuits adapted to produce reliable actuation of the toggle during clearing 'of toggle to one of its two states or transferring information into and out of the toggle.

A toggle is a binary device in that one section or tube of an electron tube toggle is always conducting and the other section is cut off. It has two stable states;

that is, either section may become conducting and the other out off. One of the states may be chosen to represent binary l, the other to represent binary 0. Toggles may be of several different designs. In a symmetrical toggle, the circuits associated with both tubes are substantially identical. An asymmetrical toggle has been designed by the present inventor in which the grid of one tube is grounded, while the grid of the other tube may be raised above or lowered below ground potential.

In computer terminology, a toggle is cleared to 0 when the toggle is forced to assume the state arbitrarily selected to represent 0. Information is said to be transferred into a toggle when the toggle is set to the state corresponding to the number constituting the information. Transfer out of a given toggle generally contemplates setting another toggle or memory device in accordance with the state existing in the given toggle.

One conventional way to clear a toggle is to lower the voltage at one control grid, driving that section or tube below cut off. A negative pulse to accomplish the clearing action may be coupled to the toggle through a cathode follower stage. To transfer information in or out of a toggle, simultaneous clearing action is also generally provided, for convenience in circuit design. If information is to be transferred into a group of toggles, then it is desirable for all toggles to be first cleared to the same state, so that they may be reset or left undisturbed, according to the character of the information, by tripping or not tripping the respective toggles with a transfer pulse. If information is to be transferred out of a toggle, then it may be desirable to leave that toggle in a predetermined state to prepare it for receipt of the next bit of information.

Accordingly, it is an object of the present invention to provide a novel electronic storage device including means for access to information stored therein.

A further object of the invention is to provide a method of and means for driving an electronic toggle without interfering with proper toggle operation.

Yet another object of the invention is to accomplish the above-stated objects with a minimum number of circuit components consistent with reliability of overall operation.

Further objects and advantages of my invention will become apparent from the following detailed description of a preferred embodiment of the invention, when read in connection with the appended drawings, in which:

Patented June 10, 1958 Figure 1 illustrates schematically an asymmetrical toggle circuit,

Figure 2 illustrates schematically a symmetrical toggle circuit, and

Figure 3 illustrates schematically control and access circuits for the storage unit constructed according to the principles of the invention.

In the present invention, an input pulse signifying a transfer order is caused to produce two pulses: a first or clear pulse beginning at substantially the same time but ending slightly sooner than the second or transfer output pulse. The toggle driven is caused to assume a selected state because the clear pulse is coupled to and acts directly on one grid and the opposite plate of the toggle. The transfer output pulse is generated and may be applied through a gating device and driver tube to the cathode of the toggle to transfer information in, or through agate it may actuate a toggle monitoring tube to transfer information out. The memory effect of the driver and the longer pulse impressed thereon will cause the transfer outputpulse to be effective after the clear cycle is complete, in the case of a transfer in.

To drive toggles in the manner of the present invention, certain voltage levels must not be exceeded by the incoming, driving pulses to avoid drawing excessive grid current or otherwise interfering with toggle operation. To minimize fluctuation of the driving voltages, the present inventor provides novel self-regulating driver circuits for actuating the toggles. Only those voltage levels which are important for the reliability of the toggle are regulated, to simplify circuit design and to reduce the number of components required.

Referring now to Figure 1, tubes 2, 3 have a common cathode 6, which is returned through resistor 9 to the negative side of a 300 volt supply. Grid '5 is connected to ground, while grid 8 is coupled to "a junction in the divider network including resistors 10, 1'1, 12. When tube 2 conducts, grid 8 will assume a potential lower than that of cathode 6, cutting off tube 3, because of the voltage drop across resistor 10. Conversely, if tube 2 I is cut off, grid 8 will assume a potential higher than that of cathode 6, and tube 3 will conduct. Cathode 6 will rise above ground potential to follow grid 8, thus tending to keep tube 2 cut off. The toggle may represent 0" when tube 2 is conducting and 1 when tube 3 is conducting.

Tube 13 is a monitor for the toggle, its .grid 14 being coupled to grid 8 and being high or low as tube 3 is conducting or cut off. Tube 13 is energized from a source of volts and has its cathode returned to transfer out bar 15 through a resistor gate 16, 17. To the output of the gate is coupled grid 18 of tube 19, which is supplied from a source of +110 volts and may deliver an output signal from its cathodeZtl at terminal 21 when pulsed by a transfer pulse on lead 15'.

Transfer of information in m'ay be accomplished through input terminal 22, to which is coupled resistor gate 23, 24. The gate may be pulsed on transfer lead 25 and determine the voltage on grid 26 of tube 27, the cathode 23 of which is coupled to cathode 6. Tube 27 is energized from a source of +110 volts and is normally not conducting. The toggle is first cleared to 0, so that tube 2 is conducting. Coincident positive signals on leads 22, 25 will raise grid 26 above cut off, raise the cathodes 28, 6 above the potential of grid 5, cut off tube 2, and flip the toggle to the desired 1 state.

The symmetrical toggle of conventional design as shown in Fig. 2 is essentially the Eccles-Jordan trigger circuit, and is described in the Sixth Interim Progress Report of the Institute for Advanced Study, by C. V. L Smith. It will be apparent to those skilled in the art that the teachpulse.

ings of the present invention are applicable as well to the symmetrical toggle, and pulses of the required amplitude can be readily obtained by adjustment of the circuit pafurnishes the plate load for tube 32 and is coupled to a source of +150 volts. The grids of twin triode 33 are joined and coupled to the plate of tube 32. The cathodes and plates are also joined respectively, and the cathodes are coupled to the high-potential end of coil 34 while anodes are coupled through a condenser 39 to the grid of tube 32 and to the input of the driver circuit 40.

The driver circuit 40comprises a cathode-coupled pair of tubes 42, 43, triodes 44, 45, twin triodes 46, 47, and associated circuits. Triode 42 is supplied from a source of +110 volts, its cathode is returned to 300 volts through resistor 48, and its grid potential is determined by the output potential of the pulse former 30. Triode 44 is supplied from a source of +220 volts, its grid is coupled to the cathodes of triodes 42, 43, and its cathode is returned to ground. The grids of triodes 46, 47 are coupled to the plate of triode 44, while their anodes are supplied from a source of +220 volts, and their cathodes are coupled to output lead 49. The plate of triodes 45 is also coupled to lead 49, its grid is coupled to the plate of triode 43, and its cathode is returned to ground. Grid .bias is provided through diode 50, the plate of which is coupled to a source of 1S volts. The cathodes of parallel-connected triodes 46, 47 are returned to a source of 300 volts through resistors 51.

Driver 41 is adapted to regulate the top of an output Triodes 52, 53 are cascaded to form a unit-gain electronic voltage divider deriving potential from sources of +220 volts and 300 volts coupled to the plate of triode 52 and the cathode of triode 53, respectively. Resistors 54 couple the tubes together and are shunted by condenser 55. Input triode 56 is energized from the same source of +220 volts as is triode 57, which is cathode coupled to triode 58 to form a difference amplifier. The grid bias on triode 58 is furnished from the common cathode return source of 300 volts through resistor 59 and may be varied by adjustment of potentiometer 60. Plate voltage is supplied from a source of +110 volts. Twin triode 61 is supplied plate voltage from a source of +110 volts, its grids are coupled to the plate of triode 53 through limiting resistors, and its cathode coupled to the grid of triode 57 and also returned through a resistor 62 to a source of 300 volts. Bias for triode 53 is supplied from the cathode return source of -300 volts through resistor 63. Resistor 64 couples the grid of triode 53 to ground.

Referring now to Figure 3, when a transfer operation is desired, a pulse appears on lead 65. The pulse may be negative, going from +30 to -20 volts, for example.

The pulse is impressed on tube 56, which is normally con ducting, and cuts it off, producing a positive pulse at the anode thereof which is coupled to the grid of tube 52. A

resulting positive pulse from the cathode of tube 52 is I tube 61, decreasing current flow therethrough, and lowering the potential at output 66 to the desired level.

As above stated, the two tubes 52, 53 in cascade form a unit-gain electronic voltage divider. Tube 53 is a constant current tube with the plate current entirely dictated by the cathode voltage and cathode resistor. Therefore, substantially the entire voltage swing occurring at the cathode of tube 52 will be almost exactly reproduced at the anode of tube 53, within the linear characteristics of the tubes. The two equal resistors 54 in series provide the required voltage level shift.

The pulse former circuit also receives the pulse from input 65 and utilizes it to deliver a positive output pulse to the driver 40. The positive swing of the pulse is limited by coupling condenser 39 back to the grid of tube 32 and by the coupling of cathode of tube 33 to a source of fixed potential, so that the grid bias of tube 33 is determined by the negative swing of the anode of tube 32.

The positive pulse resulting when tube 33 is cut off is coupled through condenser 39 to tube 42, producing a positive pulse at the grid of tube 44 and a positive pulse at the grid of tube 45, as tube 43 is cut off. Tube 44 delivers a negative pulse to the grids of tubes 46, 47, connected in parallel. An output signal is taken from the cathodes of the two last named tubes on lead 49. Should the lower potential of the output pulse attempt to go below +50 volts, the decrease in potential would be coupled to the grid of tube 43, lowering its cathode potential and the grid potential of tube 44, thus increasing the grid potentials of tubes 46, 47. Therefore, tube 46, 47 will be driven less negative, allowing their cathodes to remain at +50 volts potential as desired.

Having thus described my invention, I claim:

1. A bistable electronic toggle comprising a pair of interconnected electron tubes each including cathode, grid, and anode electrodes, the grid of a first tube being coupled to the anode of the second tube, a source of positive energizing voltage for said second tube coupled to its. anode and comprising an output cathode follower, a first amplifier stage supplied with current from said follower, a second amplifier coupled to drive said follower, a first differential amplifier provided with one input coupled to said follower, a second input coupled to a normally constant reference voltage, and a pair of outputs coupled to control said first and second amplifiers, respectively, and means responsive to a control pulse for momentarily lowering said energizing voltage to cut off said first tube comprising a second differential amplifier coupled to receive said pulse at one input and coupled to said normally constant reference voltage at the other input, and a third amplifier stage deriving its input from the output of said second dilferential amplifier and coupled'at its output to the normally constant reference voltage to change the same momentarily upon receipt of a pulse from said second differential amplifier.

2. A bistable electronic toggle comprising a pair of interconnected electron tubes each including cathode, grid, and anode electrodes, the grid of a first tube being coupled to the anode of the second tube, a source of positive energizing voltage for said second tube coupled to its anode and comprising an output cathode follower, a first amplifier stage supplied with current from said follower, a second amplifier coupled ,to drive said follower, a first difierential amplifier provided with one input coupled to said follower, a second input coupled to a normally constant reference voltage, and a pair of outputs coupled to control said first and second amplifiers, respectively, means responsive to a control pulse for momentarily lowering said energizing voltage to cut off said first tube comprising a second diflerential amplifier coupled to receive said pulse at one input and coupled to said normally constant reference voltage at the other input, and .a third amplifier stage deriving its input from the output of said second differential amplifier and coupled at its output to the normally constant reference voltage to change the same momentarily upon receipt of a pulse from said second difierential amplifier, and means for actuating said toggle responsive to said control pulse comprising a second cathode follower having its cathode coupled to an appropriate electrode of one of said tubes to deliver a pulse to the same, a third differential amplifier deriving one input from said third follower and another input from a reference voltage source, a constant-current voltage divider comprising a pair of cascaded electron tubes, each tube being provided with anode, grid, and cathode electrodes, the anode of one of said cascaded pair being coupled to the cathode of the second of said cascaded pair, means coupling said last-named anode to the input of said second follower to control conduction therethrough, a fourth amplifier provided with an input coupled to receive said control pulse and an output, and means coupling the outputs of said fourth amplifier and said third differential amplifier to the grid of said second tube of said pair, whereby an attempted rise in said follower output voltage above a selected voltage will lower the grid potential at the input to said divider and thereby lower the input voltage to said follower, effectively preventing said rise.

3. An electronic storage device'comprising a bistable electronic toggle circuit provided with a first input for receiving a reset signal to clear said toggle circuit to a first condition, a second input for receiving a gating signal to transfer information into said toggle, and a third input to receive an information signal; means responsive to a control pulse from an external source for forming a reset pulse of selected duration; a first amplitude-regulated power amplifier coupled between said pulse forming means and said first input for delivering said reset signal to said toggle circuit; circuit means operative in response to said control pulse for forming a gating signal of longer duration than said reset signal; a second amplitude-regulated power amplifier connected between said last-named circuit means and said second input to deliver a regulated gating signal to said toggle circuit; and a gating circuit including said second and third inputs to actuate said toggle circuit response to said information signal during the interval between the end of said reset pulse and the end of said gating pulse.

4. In an electronic storage device according to claim 3, the subcombination of a self-regulated power amplifying toggle driver circuit comprising an output lead, a I

first difference amplifier stage having a constant voltage input, a second input coupled to said output lead to derive a second voltage therefrom, and an output, a second driver amplifier stage provided with an output coupled to said output lead and provided with an input lead, a third amplifier stage having an input coupled to the output of said first amplifier stage and an output coupled to the input of said second amplifier stage to drive the same responsive to signals from said first amplifier, and a fourth amplifier stage having an output circuit coupled to the input of said third amplifier and an input circuit for receiving external actuating pulses, said :pulses being shaped successively in said fourth and third amplifiers and utilized to drive said second amplifiers, the output thereof being amplitude-regulated through feedback to said first difference amplifier.

5. A storage device according to claim 3 wherein said amplitude-regulated power amplifier for amplifying input pulses comprises an output lead, a first amplifier having an input circuit connected to said output lead and an output circuit, a second amplifier stage provided with an input and having an output circuit connected to said output lead, a third amplifier stage comprising two sections, each section having an input coupled to an output of said first amplifier and having respective output circuits coupled to the input of said second amplifier and to said output lead, respectively, whereby an attempted potential variation is degenerated successively through said first amplifier, one section of said third amplifier, said second amplifier, and the second section of said third amplifier to said output lead.

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